MySQL 資料查重、去重的實現語句
阿新 • • 發佈:2020-09-18
有一個表user,欄位分別有id、nick_name、password、email、phone。
一、單欄位(nick_name)
查出所有有重複記錄的所有記錄
select * from user where nick_name in (select nick_name from user group by nick_name having count(nick_name)>1);
查出有重複記錄的各個記錄組中id最大的記錄
select * from user where id in (select max(id) from user group by nick_name having count(nick_name)>1);
查出多餘的記錄,不查出id最小的記錄
select * from user where nick_name in (select nick_name from user group by nick_name having count(nick_name)>1) and id not in (select min(id) from user group by nick_name having count(nick_name)>1);
刪除多餘的重複記錄,只保留id最小的記錄
delete from user where nick_name in (select nick_name from (select nick_name from user group by nick_name having count(nick_name)>1) as tmp1) and id not in (select id from (select min(id) from user group by nick_name having count(nick_name)>1) as tmp2);
二、多欄位(nick_name,password)
查出所有有重複記錄的記錄
select * from user where (nick_name,password) in (select nick_name,password from user group by nick_name,password where having count(nick_name)>1);
查出有重複記錄的各個記錄組中id最大的記錄
select * from user where id in (select max(id) from user group by nick_name,password where having count(nick_name)>1);
查出各個重複記錄組中多餘的記錄資料,不查出id最小的一條
select * from user where (nick_name,password having count(nick_name)>1) and id not in (select min(id) from user group by nick_name,password having count(nick_name)>1);
刪除多餘的重複記錄,只保留id最小的記錄
delete from user where (nick_name,password from (select nick_name,password having count(nick_name)>1) as tmp1) and id not in (select id from (select min(id) id from user group by nick_name,password having count(nick_name)>1) as tmp2);
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